Here is how it works on the supply side. If they buy a lot of the goods in the US they now pay less for the same products. Usualy they do not pass the saving to the customer or only a portion of it. By the way you can get really hurt the other way. If your cost goes up you cannot always pass on the extra cost to the customer for many different reasons. In this case they get a double benefit. Their margins are going up, profit goes up and they double the gain when translated back in US dollars.
This is a very dangerous game for a company. You can make it one quarter and get killed the next. Double benefit goes to double loss if you reverse the currency exchange rate. This is why most companies are doing currency hedging.